Structure and magnetic properties of vanadium–sodium silicate glasses

Vanadium–sodium silicate glasses with the chemical composition [(V 2O 5) x (Na 2O) 0.30(SiO 2) 0.70− x ] (0.0⩽ x⩽0.10) have been studied by X-ray photoelectron spectroscopy (XPS) and magnetization measurements. The core-level binding energies of O 1s, V 2p and Si 2p in these glasses have been measured for surfaces produced by in vacuo fracture. The peak position and width of the V 2p 3/2 peak are independent of the V 2O 5 content while the O 1s core-level spectra show significant composition-dependent changes. Two distinct peaks are resolvable arising from the bridging oxygen and non-bridging oxygen (NBO) atoms in the silicate glasses. The fraction of NBO, determined from these spectra is found to increase with increasing V 2O 5 content in the glass and are consistent with the formation of predominantly alkali metavanadate species. The magnetic susceptibility data of these glasses indicate a large, temperature-independent diamagnetic contribution arising from the glass matrix as well as small paramagnetic contribution from the V 4+ ions. The V 4+ content deduced from the magnetization results (∼2%) is below the detection limit of XPS analysis.